.380 ACP case capacity variances

[Shuz]

In a small capacity case like the .380ACP, I am wondering if the differences in case capacity from brand to brand is important enuf to keep them separated by brand, and perhaps use a different powder charge based on the difference.

I weighed 5/ea cases of several brands and discovered a 6.4g difference in average case weight from one brand to another. In a case that only weighs roughly 50g, that's over a 10% difference!

Maybe I'm not correct in assuming case weight is in-directly proportional to case capacity; ie. heavier cases have less internal capacity.
I'd appreciate anyone who can shed light on this issue for me.--Thanks

[Outpost75]

70/30 cartridge brass is 8.58 grams/cc whereas flake pistol powders similar to 231, Bullseye or Unique are typically 0.7 to 0.85 grams/cc

there are 15.54 grains to the gram, so one cc of brass weighs 8.58(15.54) = 133.3 grains,
whereas 1 cc of 231 weighs (0.85)x15.54 = 13.2 grains,

So 6.4 grains of brass divided by 133 grains = 0.048, therefore the heavier case displaces only about 0.05 grain of powder.

The effect of the heavier case wall on proper bullet fit is more important.

[Big Boomer]

I wouldn't even jump into this at all except that I reload both 9mm and .380 (primarily I cast and reload cast boolits for both calibers but also some jacketed stuff). While the difference in case capacity may not mean much, I always segregate all my brass by headstamp except for the odd ones that I use for casual practice. My main headstamp groupings run Win., R-P, F C, Speer, Blazer (I have been told that Speer and Blazer are the same), and military, etc. Yeah ... I even keep the mil-spec cases and process them by ironing out the primer crimp. Where do those things come from, anyway? But I keep them separate. Perhaps my system is unnecessary, but it's the way I like to do things. Big Boomer

[freebullet]

If your trying to achieve max velocity then, yes sort them it might make a small difference.

For plinking loads it hasn't mattered for me.

[rking22]

I load 380s for some Berettas(84BB and 86) and I have run into issues with some brass, I am using a Ranch dog 105 from the group buy and some random cases have case walls that are so thick they buldge out when seating the bullet. Kinda looks pregnant! I set these asside and run them thru a Lee crimp die to reduce the "belly", then they go in a bag I take when walking on the farm plinking. No chance to ever see that case again in my woods!
Some of your weight variance may be in case length. My range pickups are not very consistent in length. I consider my Berettas to be very accurate for what they are, but the extent of my case sorting is separating the 380s from the durn 9mm.

[fredj338]

Maybe I'm not correct in assuming case weight is in-directly proportional to case capacity; ie. heavier cases have less internal capacity.
I'd appreciate anyone who can shed light on this issue for me.--Thanks

Maybe, maybe not. The only way to know is fill cases with powder & measure internal volume. Cases can be heavier because of the brass alloy variations, rim thickness, head thickness, the internal volume could be much closer than you think. If I were loading max pressure loads, then segregating brass by internal volume would beneficial.

[Cherokee]

Even sorting by HS will not eliminate variances. Different manufacturing lots will have variances also. Although I sort my HS, its to keep track of the number of reloads for a lot of brass. I do tend to use the same HS cases for higher end loads but not plinkers.

[Shuz]

I appreciate all the replies. Outpost75 presents an interesting analysis, but I think it may be comparing apples to oranges. So....here's what I did; I took an R-P case that weighed 45.4g and had an OAL of .667" and filled it to the brim with WC820, which is prolly the smallest granuled ball or spherical powder I have ever used and weighed the resultant powder. It weighed 12.0g.
I then took a Blazer case that weighed 51.6g and was also .667" in OAL, and filled it with the same powder to the brim. The resultant weight of powder was only 11.1g! So the difference in powder capacity between the two brands was a whopping 92.5%.This leads me to the conclusion that heavier .380 cases, like Blazer's, have a smaller powder capacity, and a load that may be safe in a R-P case, may be too hot for another "heavier" brand.

[gwpercle]

You're overthinking it .
If you want to separate cases because of OCD-Anal disorder , fine, but weighing cases and trying to adjust powder charges for each is a big waste of time and energy. What you going to do with them shoot 100 yard target matches....No, it's a 380 you going to shoot at a few feet. The differences in capacities are not enough to create dangerous pressures. I reload 25 acp , 32 acp and 380 acp and none of the small bores have had problem s related to mixed cases and pressure.
I don't bother separating, unless I get a full box from the get go.

[whisler]

"So the difference in powder capacity between the two brands was a whopping 92.5%."


Check your math. The difference in case capacity is about 8%. Or stated another way the capacity of the Blazer brass is 92.5% of the other brass.

[Outpost75]

I appreciate all the replies. Outpost75 presents an interesting analysis, but I think it may be comparing apples to oranges. So....here's what I did; I took an R-P case that weighed 45.4g and had an OAL of .667" and filled it to the brim with WC820, which is prolly the smallest granuled ball or spherical powder I have ever used and weighed the resultant powder. It weighed 12.0g.
I then took a Blazer case that weighed 51.6g and was also .667" in OAL, and filled it with the same powder to the brim. The resultant weight of powder was only 11.1g! So the difference in powder capacity between the two brands was a whopping 92.5%.This leads me to the conclusion that heavier .380 cases, like Blazer's, have a smaller powder capacity, and a load that may be safe in a R-P case, may be too hot for another "heavier" brand.

You should repeat this measurement with WATER. Then consider the bulk density of typical pistol powders you will actually be using, which will probably be LOTS less dense than 1 gram/cc, Bullseye being about 0.7 g/cc and 231 being about .85 g/cc. If you REALLY have any .380 loads for WC820 I would like to see your test data...

[Shuz]

The reason I did not use water is due to the fact that it was harder for me to measure accurately. The reason I used WC820, was that it is the densest powder I had on hand. I no way would I attempt to use WC820 in a .380ACP case!! I am merely trying to determine the relative case capacities from one brand of brass to another in order to prevent either high pressure or FTF problems.
Perhaps I'll try the same experiment with Bullseye and see if I still get about 7.5% difference in capacity.

[Outpost75]

You mean 7.5%

[Treeman]

Shuz, You didn't get 92.5% difference in capacity. One had 92.5% capacity of the other. That is an important distinction.

[HangFireW8]

You're overthinking it .
If you want to separate cases because of OCD-Anal disorder , fine, but weighing cases and trying to adjust powder charges for each is a big waste of time and energy. What you going to do with them shoot 100 yard target matches....No, it's a 380 you going to shoot at a few feet. The differences in capacities are not enough to create dangerous pressures. I reload 25 acp , 32 acp and 380 acp and none of the small bores have had problem s related to mixed cases and pressure.
I don't bother separating, unless I get a full box from the get go.

I agree with this.

After reloading a bunch of 380 and tons of 9mm, I've come to this conclusion- the real enemy is the combination of a deeper seating depth and powder variance when loading stiff loads with heavier projectiles.

If you happen to load some 380 where the powder charge sometimes varies to the high side (it happens, particularly on progressives), and a few of the bullets seat on the deep side, when both happen at once you can end up with a real "Zinger". Jacketed Hollow Points in particular vary more in seating depth from load to load.

On top of that, progressives will vary seating depth by as much as .010" depending on the number of shells on the plate due to compression. Even if you bear down on the compound leverage handle, with more shells on the shellplate, the cartridges will be on the long side. Run just one through alone, on the shorter side. I came to this conclusion taking many measurements on my old Hornady Projector, then read an article where someone came to the same conclusions on a Dillon 550B.

[FISH4BUGS]

I cast (H&G S55 10 cavity) and load 380 for the M11A1 Mac submachinegun. It could care less. I just make sure there is a Lee FCD in station 4 of the Dillon 550. That takes care of any bulging issues. Otherwise, don't load to max+ and the tiny variations in case capacity should make no difference whatsoever.

[Bigslug]

For the benefit of safety, do your load workup in the heavier cases and never think of it again. Yeah, you'll get more variation than you will with a low pressure round like .44 Special or .45 ACP, but then again, you aren't shooting Bullseye matches with a .380. The soda can at 15 yards will never know the difference.

[Shuz]

I'm gonna do what Bigslug suggests and do the load work up in the heavier brass, and test the same load in the lighter brass to make sure the action still functions properly. My .380's are just carry guns that I hope to never use for "close social work", but one is always handy. Much easier to conceal than my favorite carry gun, a S&W 329PD in .44 mag! Thanks for all the replies and suggestions!